Charged Polarons and Molecules in a Bose-Einstein Condensate

Ultracold hybrid ion-atom gases represent an exciting frontier for quantum simulation offering a new set of functionalities and control. Here, we study a mobile ion immersed in a Bose-Einstein condensate and show that the long-range nature of the ion-atom interaction gives rise to an intricate interplay between few- and many-body physics. This leads to the existence of several polaronic and molecular states due to the binding of an increasing number of bosons to the ion, which is well beyond what can be described by a short-range pseudopotential. We use a complementary set of techniques including a variational ansatz and field theory to describe this rich physics and calculate the full spectral response of the ion. It follows from thermodynamic arguments that the ion-atom interaction leads to a mesoscopic dressing cloud of the polarons, and a simplified model demonstrates that the spectral weight of the molecules scale with increasing powers of the density. We finally calculate the quantum dynamics of the ion after a quench experiment.

Automated summary

This study investigates a mobile ion immersed in a Bose-Einstein condensate, revealing the intricate interplay between few- and many-body physics due to the long-range nature of the ion-atom interaction. Various techniques are used to describe the rich physics and calculate the full spectral response of the ion. It is shown that the ion-atom interaction leads to the existence of polaronic and molecular states, with the spectral weight of molecules scaling with increasing powers of density.